Corn Countdown

This practice sets the stage for higher yields

Weston Wiler will tell you that counting corn adds up to a better crop. Each season, Wiler evaluates his fields by taking corn stand and ear counts throughout his 4,000-plus-acre corn crop, grown in the rolling hills of south-central Michigan, near Hillsdale.

The resulting information helps him determine a variety of things, from how well he and his crew planted the crop earlier that spring to what he might anticipate for yield results at harvest.

Early summer signals the start of the process, with Wiler making random stand counts when the young corn is at the V3 or V4 growth stage.

"Everything you do is important, but that split second you go across that ground planting will define your level of success for the entire year with that crop," Wiler says.

His goal at planting is to establish good seed-to-soil contact. That and even planting depth contribute to uniform emergence, which leads to what Farm Journal Field Agronomist Ken Ferrie likes to call photocopied plants and ears.

Row spacing

Row length

40"

13' 1"

36"

13' 6"

30"

17' 5"

22"

23' 9"

15"

34' 10"

Use a tape measure to mark off the row length that corresponds with row spacing. Length of row equals 1/1000 of an acre.Source: University of Minnesota Extension Service

"Comparing corn stands to a picket fence is a way to measure how you did with seed singulation," Ferrie says. "Planter performance should be precise to give each plant an equal chance."

To consistently achieve uniform stands, Wiler says, he has slowed his planter down to nearly a walking speed.

"Maybe it takes an extra 20 minutes to plant a field, but what we get in return in ear count makes that additional time seem trivial," he says.

Uniform plant stands have a domino effect by contributing to the quality of corn ears.

Corn ear numbers are a good indicator of the yield potential of the field because yield is based on the number of ears per acre and the size of the ears (number of rows around, kernels long and kernel depth).

Make it count. Wiler conducts corn ear counts each August and spends an average of three days per season on the process. Last year, he and four employees did ear counts on every farm that Wiler leases.

"We did a spot sample on every farm; we probably checked 100 fields," Wiler explains. "We were scouting for weeds and insects at the same time, so while it was a big undertaking, it was fairly efficient."

Wiler uses the following process to estimate corn yield potential:

Use a tape measure to mark off 17'5" in 30" corn rows.

Count the number of corn plants in the measured-off space. Subtract any corn plants that appear unlikely to produce a good, harvestable ear.

Use stalk diameter and plant spacing to help determine harvestable ears.

"A skinny stalk diameter when compared with neighboring plants indicates that particular plant is behind in maturity and will have trouble pollinating or will produce a very small ear and isn’t something we want to count," Bauer says.

To evaluate plant spacing, look for double drops, which indicate two seeds were metered together by the planter, Bauer says. This situation usually results in two plants that will compete too much for available nutrients, and neither one will end up producing a large, harvestable ear.

Once you determine the number of harvestable ears in the measured-off space, randomly select three to five ears to count rows around and kernels long and use the following formula to arrive at anticipated yields:

Average ears x Average rows around x Average kernels long ÷ 90 = Yield

Using 32" row spacing, 16 rows around and 35 kernels long, the formula looks like this:

32 x 16 x 35 ÷ 90 = 199 bu. per acre

Bauer encourages farmers to implement this practice in four or five different locations within each field, and then average the numbers to arrive at a fairly accurate, comprehensive yield estimate.

"Keep in mind the formula does not take into consideration kernel depth," she says. "Based on weather conditions during kernel fill, you may increase or decrease your yield by 5% to 10%."

Hand in hand. As farmers evaluate plant stand numbers and ear counts, Bauer says, they can benefit from getting those two numbers to more closely align with each other.

"You want to minimize the difference between plant count and ear count numbers," Bauer says.
For example, she adds: "If you have 30,000 plants per acre and your ear count is only 27,000 ears per acre, you have the potential to increase yields 15 bu. to 21 bu. per acre by increasing your ear count to 30,000 ears per acre."

Bauer says that while the number difference between plant stands and ear counts cannot be eliminated, it can be minimized. She says that in a corn-soybean rotation, the difference between the two is ideally no more than 1,200. In corn-on-corn, with heavy residue conditions, Bauer says, the ideal difference between the two is 2,000 or less.